RXR-ALPHA REGULATES CARDIAC NEURAL CREST CELL MIGRATION

心脏神经脊细胞对于心脏的正常形成和单个心腔的成熟是必需的。特别是，这些细胞参与流出道和主动脉弓动脉的形成。对这些细胞的需求已经在鸡的神经脊消融研究中得到了最好的证明，这会导致各种心脏畸形，包括PTA，VSD和DORV。有趣的是，这些缺陷类似于临床上看到的各种形式的先天性心脏病。此外，过量的维甲酸(RA)或维生素A缺乏都会导致相似的表型，提示RA也可能参与心脏神经脊的迁移和/或分化。此外，已有研究表明，RA受体RXRpha的突变导致相似的心脏表型，这表明调节心脏神经脊细胞谱系的RA信号通路是通过RXRpha介导的。因此，研究中的假设指出，在RXRpha突变体中检测到的流出道缺陷是心脏神经脊细胞迁移缺陷的结果。已经设计了两个具体的目标来检验这一假设。(1)通过(A)分子标志物分析和(B)指示小鼠品系，确定在RXRpha缺陷胚胎中发现的流出道缺陷是否是心脏神经脊细胞迁移缺陷的结果；(2)通过(A)RXRpha与心脏神经脊细胞共定位，(B)神经管外植体培养和(C)分析RXRpha心脏神经脊限制缺陷小鼠的心脏神经脊细胞迁移和流出道缺陷，确定神经脊细胞迁移缺陷是细胞自主还是非细胞自主的。

The cardiac neural crest cells are necessary for proper heart formation and maturation of individual cardiac chambers. In particular, these cells are involved in the formation of the outflow tract and aortic arch arteries. Requirements for these cells has been best demonstrated by neural crest ablation studies in the chick which results in a variety of cardiac malformations including PTA, VSD, and DORV. Interestingly, these defects resemble various forms of congenital heart disease seen in the clinical setting. In addition, both an excess of retinoic acid (RA) or vitamin A- deficiency leads to similar phenotypes suggesting that RA may also be involved in cardiac neural crest migration and/or differentiation. Furthermore, it has been shown that mutations to the RA receptor RXRalpha lead to similar cardiac phenotypes suggesting that RA signaling pathways regulating the cardiac neural crest cell lineage are mediated via RXRalpha. Therefore the hypothesis under investigation states that outflow tract defects detected in the RXRalpha mutant result from defects in cardiac neural crest cell migration. Two specific aims have been designed to test this hypothesis. (1) To determine if the outflow tract defects found in the RXRalpha deficient embryos is the result of defects in cardiac neural crest cell migration by (a) molecular marker analysis and (b) indicator mouse lines; (2) To determine if the defect in neural crest cell migration is cell autonomous or non-cell-autonomous by (a) co-localization of RXRalpha to the cardiac neural crest cells, (b) neural tube explant cultured and (c) analyzing cardiac neural crest cell migration and outflow tract defects in mice harboring a cardiac neural crest restricted deficiency in RXRalpha.